Method for automatic sea lice monitoring in salmon aquaculture

ABSTRACT

The present invention pertains to a method for automatic sea lice monitoring in fish aquaculture, the method comprising submerging a camera (4) in a sea pen (300) comprising fish, using the camera to make an image of at least one of said fish, analysing the image to differentiate between individual sea lice present on the fish and the fish itself and assessing the number of sea lice present on the fish, wherein the camera is attached to a device (1, 10, 100) for guiding the salmon along an imaging track (5), the camera being directed to the track.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation application of U.S. application Ser.No. 16/951,338, filed Nov. 18, 2020; which is continuation applicationof U.S. application Ser. No. 15/767,888, filed Apr. 12, 2018 whichissued as U.S. Pat. No. 10,863,727 on Dec. 15, 2020; which is a U.S.National Phase entry under 35 U.S.C. § 371 of PCT/EP2016/075385, filedOct. 21, 2016; which claims priority to EP Application No. EP15191108.8,filed Oct. 22, 2015; the content of each of which is hereby incorporatedby reference in its entirety.

GENERAL FIELD OF THE INVENTION

The present invention pertains to a method for automatic sea licemonitoring in fish aquaculture, such as salmon aquaculture, the methodcomprising submerging a camera in a sea pen comprising salmons, usingthe camera to make an image of at least one of said salmons, analysingthe image to differentiate between individual sea lice present on thefish, such as salmon and the fish itself, and assessing the number ofsea lice present on the salmon. The invention also pertains to a systemfor use in fish aquaculture to automatically monitor and report sea licepresence on fish, and to a device for making images of fish present in asea pen.

BACKGROUND ART

Regular and accurate sea lice monitoring is a vital component to anyeffective integrated pest management regime targeted against one of themost costly ectoparasitic pathogens associated with modern fishaquaculture such as salmon aquaculture. In most regions with substantialcultured salmon production, sea lice (mainly Lepeophtheirus salmonis andvarious Caligus species) continue to be one of the most important fishhealth concerns. Even in regions where significant infestations tend notto be experienced, such as British Columbia or the far north of Norway,it is important to monitor sea lice levels to mitigate any potentialnegative impacts for wild salmon. In addition to regular monitoring, therecent emergence in a number of regions of tolerance to certainchemotherapeutants has emphasised the importance of methods to obtainaccurate sea lice estimates before and after treatment to properlyassess the efficacy of any medication being used so as to gain earlywarning of tolerance issues. However, to date, this involves a manualprocess which is time consuming and dependent for its accuracy on theskill of the individual carrying out the count and their ability toaccess a range of sea pens. Crowding fish within pens to select arepresentative sample also imposes stress on these fish. Because of thetime required only a small number of fish can be sampled. However, aslice numbers have been driven down over the past decade, increasinglylarge samples are required to maintain the statistical reliability ofany population-level estimates.

The use of underwater imaging has therefore been proposed as anautomated and passive counting system. Creating an image of a fish suchas salmon covered by sea lice (which image may be part of a video, whichvideo technically is a series of images) provides the possibility ofautomatically monitoring the number of sea lice on fish. It is possibleto differentiate between individual sea lice present on a fish such assalmon and the (skin of the) fish or salmon itself, thus to distinguishbetween individual sea lice present on the skin of a fish or salmon andthe skin of the fish or salmon itself. This way, the number of sea licepresent on one fish or salmon can be assessed. One of the key projectsto practically develop such an imaging method was the EurostarsVisuaLice project, which was a follow up innovation of a pilot study byScottish researchers in 2005-2007. As stated in the Executive Summary ofthe 2013 report of VisuaLice (Population Interpretation of Passive SeaLice Monitoring, authors Cox and Revie) to the Havbruksinstituttet andFHF Norway, such a system can offer the benefits of enhancedrepeatability and accuracy, larger sample sizes, continuous monitoring,lower costs and lower levels of disturbance to the fish. It wastherefore proposed in the project to develop such a system to assess therelative value of this novel approach in comparison to traditionalmanual counting. However, although it appeared to be possible todistinguish individual sea lice present on the skin of a fish or salmonusing commonly known imaging techniques, results from experiments andfield trials of the underwater imaging system were largely unsuccessful.

OBJECT OF THE INVENTION

It is an object of the invention to devise a method for automatic sealice monitoring that can successfully be used to assess the number ofsea lice present on fish such as salmons present in sea pen. It isanother object of the invention to devise a system for use in fishaquaculture such as salmon aquaculture to automatically monitor andreport sea lice presence on salmons.

SUMMARY OF THE INVENTION

In order to meet the first object of the invention, a method as outlinedin the GENERAL FIELD OF THE INVENTION section here above has beendevised, wherein the camera is attached to a device for guiding the fishsuch as salmon along an imaging track, the camera being directed to thetrack. Using a prior art method, the principal problem is not that sealice cannot be distinguished on a fish such as salmon for accuratecounting, the problem is that the fish do not appear on the images in astandardised way, for example, the angle and distance may varyconsiderably depending on the spatial relationship between the cameraand the fish at the time of making an image. Also, in many instances fartoo many fish appear on an image, partly overlapping each other. This onthe one hand makes the automatic sea lice monitoring less easy, but moreimportantly, may prevent that a complete side surface of a fish such asa salmon can be assessed. All of this contributes to less reliability.

By using the device as specified, the camera holds a predeterminedposition with respect to an imaging track (i.e. a path or line alongwhich a fish or salmon may swim, to which path or line the camera isdirected to be able and image the fish or salmon when actually passing).Even though the track may be wider than the width of just one fish suchas salmon, this way the imaging of the fish may take place withsubstantially improved reliability. This is because the distance andorientation of the fish with respect to the camera is better controlledwhen compared to a method wherein a camera is simply submerged in thesea, without being spatially positioned with respect to an imaging trackand thus, with respect to a fish such as salmon to be imaged. Also, thechance that an image of fish overlapping each other is decreased, whichalso contributes to an improved reliability of the automatic monitoringmethod.

In order to meet the second object of the invention a system is devisedcomprising a central processing unit (CPU), and connected to the CPU acamera submerged in a sea pen comprising the fish such as salmons, thecamera being devised to make images of said fish or salmons, wherein thecamera is attached to a device for guiding the fish or salmons along animaging track of this device, the camera being directed to the track,imaging software running on the CPU to analyse images of the fish orsalmons made by the camera, to differentiate between individual sea licepresent on each of the said fish or salmons and the fish or salmonsthemselves, and to assess the number of sea lice present on the fish orsalmons, and a reporting unit connected to the CPU, to display a resultscorresponding to said assessing. This system makes use of the sameadvantages of the imaging device as described here above.

The invention also enables the use of a device for making images of fishand especially salmons present in a sea pen, the device comprising atrack for guiding a fish or salmon through the device, the devicecomprising an enclosure that confines the track, wherein the camera isattached to the enclosure and directed to the track.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A-1C show devices for use in the present method.

FIG. 2 schematically shows a system according to the invention.

FIG. 3 shows a device according to the invention, spatially fixed withregard to the walls of a sea pen for cultivating salmons.

FIGS. 1A-1C

FIGS. 1A-1C shows three devices for use in the present method. In FIG.1A a simple open triangle 1 is depicted, comprising two legs 2 and 3,having a length of about 50 cm. Within the try square of the triangle,imaging track 5 (which is viewed from the back in this figure) isdepicted. Cameras 4 and 4′ are directed to this track. The triangle legswill typically prevent that salmons will swim very close to the legs,they will keep a certain distance. This distance is such that itcoincides with the distance between the track and the two legs. Thisway, occasionally a salmon will swim along the imaging track. Uponpassing the cameras, one or more pictures (or a short film) will betaken for image analysis.

An improved device is depicted in FIG. 1B. This device 10 has as a corepart a cylindrical tube 11, which tube represents a radial enclosure toconfine the imaging track 5. At its distal end, the tube 11 is providedwith a funnel 12 to guide a salmon towards the tube 11. The diameter ofthe core is such that a salmon will not enter the core at the non-funnelside, since the salmon will notice the walls of the tube (for a salmonof 3-4 kg this may be a diameter of about 20-25 cm). However, at thefunnel side, once entered the device, a salmon will not turn whenreaching the tube 11 and will swim through, in essence following theimaging track 5. Two cameras 4 and 4′ are directed towards this track.The device is also equipped with a thermometer 6 to measure thetemperature of the sea water at the time of taking pictures (images) ofthe salmon.

Another type of device is depicted in FIG. 1C. This device 100 comprisesan endless circular frame enclosing an imaging track 5. To the frame areconnected two cameras 4 and 4′, and a thermometer 6, corresponding tothe same elements as depicted in FIG. 1B. The diameter of the frame ischosen such that a salmon will swim through the device from either sideand be guided in essence along (i.e. coinciding with or at leastadjacent) the imaging track. For a salmon having a weight of 3-4 kg, atypical diameter is 40-60 cm (depending also on the density of salmonsin the pen). In an embodiment (not shown), the frame is provided withmeans to adapt the circular width to the size of the salmons in a pen.At the bottom of the frame, indications of length 7 are provided toserve as a ruler.

In particular for the devices having a radially enclosure for theimaging track, smaller versions may be made to learn young salmons inhatcheries to get comfortable with swimming through the device. This maylead to an ultimate device (i.e. a device for use in the actual sea pento grow the salmons) having minimum radial dimensions, therebyincreasing the intrinsic reliability of the method.

FIG. 2

FIG. 2 schematically shows a system according to the invention. Thesystem comprises a central processing unit (CPU) 200 and via data line207 (which may be a wireless connection) connected to the CPU the device100 (see FIG. 1C) submerged in a sea pen comprising the salmons (notshown; see FIG. 3 ). The cameras of the device 100 are devised to makeimages of the salmons when they swim along the corresponding imagingtrack. The CPU comprises imaging software running on the CPU to analyseimages of the salmons made by the camera, to differentiate betweenindividual sea lice present on each of the said salmons and the salmonsthemselves, and to assess the number of sea lice present on the salmons.For this, the CPU makes use of a memory 202 which via line 201 forms apart of the CPU as a whole. Data is reported via lines 203 and 205 tothe regulating authorities 204 and/or farmer 206 respectively.

FIG. 3

FIG. 3 shows a device 100 according to the invention, spatially fixedwith regard to the walls of a sea pen 300 submerged in the sea 301. Thedevice 100 is coupled to an anchor 401 that is attached to the bottom ofthe sea pen 300. Next to this, the device is coupled via two dampedlines 402 and 402′ to sites of the wall of the pen near the surface ofthe sea. This makes sure that the device will not bounce with respect tothe pens itself, thereby increasing the chance that salmons will beguided along the imaging track.

Definitions

Automatic means without requiring operator intervention to perform theaction. This does not exclude that an automatic action may be initiated(for example requested), intervened or terminated by an operator.

Radial means heaving walls or borders arranged around a centre.

Assessing a number of items means to create a parameter that correspondsto that number of items, for example by explicitly counting the numberof items or by establishing the total weight of the items.

A central processing unit is a hardware system, programmed to processdata. The hardware does not need to be one single unit, but may compriseseveral distributed units operatively connected via for example wirelessconnections.

An enclosure of a track means that the items that should pass the trackcannot freely cross the enclosure. This does not include that othermaterial (for example units smaller than the items, or a liquid or gas)can cross the enclosure.

A camera being directed to an item means that the camera is positionedto be able and make an image of that item or a second item positioned ina straight line between the camera and the said first item.

EMBODIMENTS OF THE INVENTION

In an embodiment of the invention the device comprises a radialenclosure to confine the track. It was found that a very convenient andreliable way of guiding a fish, such as salmon along an imaging track isto use a device that radially confines the track. The width of theopening should be chosen such that the salmon is typically not hinderedin swimming along the track, but also, not too big to prevent improperguidance. The actual measures to allow a fish or salmon to swim throughthe device, and still give adequate guidance is believed to dependmainly on the age (size) of the fish or salmons and the density of thefish or salmons in the pen. Good results were obtained when the radialenclosure has a diameter or diagonal that is about 90-150% of the girthof the fish. The girth of the fish is the distance of the circumferenceof the fish going round the fish from the back to belly and back to theback of the fish and is the distance around the fattest, thickest orbiggest part of the fish, which is usually the midsection. Girth may bemeasured with a fabric ruler, or using a string, and then measuring thelength of the string. Preferably, the diameter or diagonal of theenclosure is 90-150% of the girth of the fish. More preferably, thediameter or diagonal of the enclosure is 100-140% of the girth of thefish, more preferably, the diameter or diagonal of the enclosure is105-130% of the girth of the fish, more preferably, the diameter ordiagonal of the enclosure is 110-125% of the girth of the fish, morepreferably, the diameter or diagonal of the enclosure is 115-120% of thegirth of the fish. The above measures ensure the free movement of thefish, and the fish will swim freely along track, without needing anyforce. It is important for the fish to swim freely, into the device toavoid any stress. If no force is needed for the fish to swim into thedevice and along the track, then the fish will experience less stress,which is beneficial and no additional devices are needed to force thefish into the device and along the track. The above measures also ensurethat the fish swim through the enclosure one by one, thereby avoidingoverlap of fish that will compromise the counting. In addition, theabove measures have the benefit that the fish will swim through theenclosure in a uniform way. This has the advantage that the cameras maybe aligned in the most beneficial way to count the sea lice and that foreach fish the sea lice are counted at the same part of the fish for eachfish, thus ensuring uniform and thus reliable counting.

In another embodiment the enclosure is circular enclosure. A circularenclosure is easier to position evenly around a longitudinal imagingtrack, increasing the reliability of the method. In yet anotherembodiment the enclosure is endless along its circumference, i.e. nothaving an opening to interrupt the circumference. This provides for animproved stability of the device. In still another embodiment the deviceis a circular frame. Such a frame has been found ideally suitable toguide a fish such a salmon over a track corresponding to the axis of theframe. For a circular enclosure preferably, the diameter of the circularenclosure is 90-150% of the girth of the fish. More preferably, thediameter of the circular enclosure is 100-140% of the girth of the fish,more preferably, the diameter of the circular enclosure is 105-130% ofthe girth of the fish, more preferably, the diameter of the circularenclosure is 110-125% of the girth of the fish, more preferably, thediameter of the circular enclosure is 115-120% of the girth of the fish.

In an embodiment the device is spatially fixed with regard to one ormore walls of the sea pen. Would the device be mechanically connected toa float, the submerged device would bounce with the amplitude of thewaves. It is foreseen that this creates too much disturbance around thedevice, possibly keeping the salmons away from taking the imaging track(depending on the amplitude of the waves). By spatially fixing thedevice with respect to one or more walls of the pen, for example withrespect to the bottom of the pen using an anchor that grasps thisbottom, this potential problem may not arise.

In another embodiment the device comprises at least two cameras directedto the track. Using two or more cameras enables a greater surface of thesalmon to be images, thereby increasing the reliability of theassessment of the number of sea lice present on the salmon.

In still another embodiment the device is provided with a thermometer torecord the sea water temperature at the time the image is made. The seatwater temperature is an important factor in sea lice infestations. Byrecording the sea water temperature, the relation between temperatureand sea lice infestations can be better assessed.

In yet another embodiment, in addition to the number of sea lice presenton the fish such as salmon, the size of these lice is assessed. Thisway, information about the stage of life of the sea lice can beobtained. This can be important information to optimize combatting aninfestation of sea lice in a pen.

Another aspect of the invention is directed to a system for use in fishaquaculture to automatically monitor and report sea lice presence onfish, the system comprising

-   -   a central processing unit (CPU; 200)    -   connected to the CPU a camera submerged in a sea pen comprising        the fish, the camera being devised to make images of said fish,        wherein the camera is attached to a device for guiding the fish        along an imaging track of this device, the camera being directed        to the track,    -   imaging software running on the CPU to analyse images of the        fish made by the camera, to differentiate between individual sea        lice present on each of the said fish and the fish themselves,        and to assess the number of sea lice present on the fish,    -   a reporting unit (204, 206) connected to the CPU, to display a        result corresponding to said assessing.

Another aspect of the invention is directed to a device for makingimages of fish present in a sea pen, the device comprising a track forguiding a fish through the device, the device comprising an enclosurethat confines the track, wherein the camera is attached to the enclosureand is directed to the track.

Optionally the enclosure is a radial enclosure (11, 101) to confine thetrack. Optionally the enclosure has a diameter or a diagonal having alength that is 90-150% of the girth of the fish. Optionally theenclosure is a circular enclosure. Optionally the enclosure is endlessalong its circumference. Optionally the enclosure is a circular frame(101).

The method, device and system of the present invention are especiallywell-suited for aquaculture where the fish are cultured in open watersuch as salmon and trout, and especially for salmon.

Embodiments and/or features as indicated for the method are expresslyenvisioned as embodiments for the device and/or system.

For the sake of conciseness not every combination of embodiments and/oroptional features are described herein, however each combination ofembodiments and/or described features are expressly envisioned in thepresent invention.

What is claimed is:
 1. Method for automatic sea lice monitoring in fishaquaculture, the method comprising: submerging a camera (4) in a sea pen(300) comprising fish, using the camera to make an image of at least oneof said fish, analysing the image to differentiate between individualsea lice present on the fish and the fish itself, assessing the numberof sea lice present on the fish, characterised in that the camera isattached to a device (1, 10, 100) for guiding the salmon along animaging track (5), the camera being directed to the track.
 2. A methodaccording to claim 1, characterised in that the device comprises aradial enclosure (11, 101) to confine the track.
 3. A method accordingto claim 2, wherein the enclosure has a diameter or a diagonal having alength that is 90-150% of the girth of the fish.
 4. A method accordingto claim 2, characterised in that the enclosure is circular enclosure.5. A method according to claim 2, characterised in that the enclosure isendless along its circumference.
 6. A method according to claim 2,characterised in that the enclosure is a circular frame (101).
 7. Amethod according to claim 1, characterised in that the device isspatially fixed with regard to one or more walls of the sea pen.
 8. Amethod according to claim 1, characterised in that the device comprisesat least two cameras directed to the track.
 9. A method according toclaim 1, characterised in that the device is provided with a thermometer(6) to record sea water temperature at the time the image is made.
 10. Amethod according to claim 1, characterised in that in addition to thenumber of sea lice present on the fish, the size of these lice isassessed.
 11. A method according to claim 1, wherein the fish is salmon.12. A system for use in salmon aquaculture to automatically monitor andreport sea lice presence on fish, the system comprising a centralprocessing unit (CPU; 200) connected to the CPU a camera submerged in asea pen comprising the fish, the camera being devised to make images ofsaid fish, wherein the camera is attached to a device for guiding thefish along an imaging track of this device, the camera being directed tothe track, imaging software running on the CPU to analyse images of thefish made by the camera, to differentiate between individual sea licepresent on each of the said fish and the fish themselves, and to assessthe number of sea lice present on the fish, a reporting unit (204, 206)connected to the CPU, to display a result corresponding to saidassessing.
 13. A device for making images of fish present in a sea pen,the device comprising a track for guiding a fish through the device, thedevice comprising an enclosure that confines the track, wherein thecamera is attached to the enclosure and is directed to the track.
 14. Adevice according to claim 13 wherein the enclosure is a radial enclosure(11, 101) to confine the track.
 15. A device according to claim 13wherein the enclosure has a diameter or a diagonal having a length thatis 90-150% of the girth of the fish.
 16. A device according to claim 13,wherein the enclosure is circular enclosure.
 17. A device according toclaim 13, wherein the enclosure is endless along its circumference. 18.A device according to claim 13, wherein the enclosure is a circularframe (101).
 19. A device according to claim 13, wherein the fish issalmon.